import java.text.DecimalFormat;
import java.util.Scanner;

public class Cube {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNext()) {
            double d = scanner.nextDouble();
            int sign = d > 0?1:-1;
            if (d <0) {
                d = -d;
            }
            boolean letter1 = d < 1;
            if (d == 0.0) {
                System.out.println("0.0");
            } else {
                if (letter1) {
                    d = 1 / d;
                }
                double c;
                c = d - 1;
                for (double i = 1.0;i <= d;i+=0.1) {
                    double cd = i * i * i -d;
                    if (cd < 0) {
                        cd = - cd;
                    }
                    if (cd > c) {
                        DecimalFormat format = new DecimalFormat("0.0");
                        if (letter1) {
                            System.out.println(format.format(sign / (i-0.1)));
                        } else {
                            System.out.println(format.format(sign * (i-0.1)));

                        }
                        break;
                    }
                    c = cd;
                }
            }


        }
    }

}
